mineral

Blue Calcite

Calcite (Calcium Carbonate, CaCO3)

Hardness: 3 on Mohs scale (soft); Color: Pale to sky blue; Luster: Vitreous to waxy/pearly; Crystal System: Trigonal; Cleavage: Perfect rhombohedral in three directions; Specific Gravity: 2.71

Hardness: 3 on Mohs scale (soft)
Color: Pale to sky blue
Luster: Vitreous to waxy/pearly

Identified March 16, 2026More mineral →

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Physical properties

Hardness: 3 on Mohs scale (soft); Color: Pale to sky blue; Luster: Vitreous to waxy/pearly; Crystal System: Trigonal; Cleavage: Perfect rhombohedral in three directions; Specific Gravity: 2.71

Formation & geological history

Formed through sedimentary processes or sometimes in hydrothermal veins; often occurs in marine environments as biological precipitates or as mineral veins in limestone and marble. Most blue specimens are attributed to the Paleozoic or Mesozoic eras.

Uses & applications

Used primarily as decorative stones, in lapidary work for carvings or cabochons, and as a popular specimen for mineral collectors. Industrially, calcite is used in building materials and pharmaceuticals, though specific blue varieties are kept for aesthetics.

Geological facts

The blue color in calcite often comes from impurities or the presence of various light-scattering inclusions. It is famous for its 'double refraction' (birefringence) property, where light splitting through a crystal creates a double image.

Field identification & locations

Identify in the field by its rhombohedral cleavage (leaning block shape), softness (can be scratched by a copper coin), and strong effervescence (bubbles) when touched with room-temperature dilute hydrochloric acid. Commonly found in Madagascar, Mexico, and Brazil.